The present invention relates generally to the field of motion picture projectors and is more specifically directed to a clutch drive mechanism for the supply and take-up film spindles of such a projector.
The use of clutches for driving supply and take-up spindles for motion picture projectors and cameras is well known in the art. One such drive is disclosed in U.S. Pat. No. 2,791,933 to Crockett. In that patent a film feed spool and a film take-up spool are connected through clutches to a motor for intermittently rotating said spools. Each spool is formed of two concentric tubes which may be of magnetic material. These tubes are secured together at one end by a flange and at the other end by an insulating ring. An annular space between these tubes contains a coil of insulated wire, the ends of the insulated wire are connected to concentric slip rings. A shaft of magnetic material is disposed axially of the spool and rotatably supported therein by a bearing at each end of the shaft. An annular space between the shaft and the inside surface of the inner tube is fitted with a Carbonyle iron powder and the tube is sealed at both ends. When a direct current flows through the coil of insulated wire a magnetic field is established through the powder which causes it to solidify and lock the spool and shaft together for conjoint rotation. Upon the coil being deenergized the powder is returned to a fluid state to permit the shaft to rotate within the tube without causing the tube to rotate.
This device, however, is complicated, requires electrical connection, is heavy and is not provided with internal braking means.
Another form of drive for film spindles is disclosed in U.S. Pat. No. 3,481,662 to Procop. Procop discloses a pair of pivotally mounted rollers for control of the supply spindle and a separate pair for control of the take-up spindle. In addition it discloses a pivotally mounted motor drive pulley to obtain directional control of an endless belt. The disadvantage of this drive mechanism is that it is complex and requires direction control of the endless belt to obtain directional control of the spindles.
A further disclosure of a clutch spindle drive means is illustrated in U.S. Pat. No. 3,677,498 to Johnson, where the amount of drive transfered between a drive motor and the film spindle is controlled by the change in weight of the reel as the film collects on the reel. The disadvantage of this mechanism is the lack of means for operator control in order to vary the transfer of motor drive to a selected spindle to obtain different modes of operation. In addition to this, since the clutch is operated by the weight of the film reel is an axial direction along the spindle axis, it would be unsuitable for conventional projectors in which the film reel weight is normal to the spindle axis.
A primary object of the present invention is to provide a new clutch and linkage arrangement with a drive belt driven in one direction only for advancing a film web in one of two different directions and at selected different speeds between a supply film reel and a take-up film reel.
Another object of the invention is to provide a new clutch and linkage arrangement for moving the film web in a selected direction and at selected operating speeds, wherein the desired operating position of the clutch and linkage arrangements are determined by movement of a single control means, which permits selection of any one of a plurality of modes of operation, such as "off", "braking", "rewind", "reverse", "forward", and "fast forward".
Still another object of the invention is to provide a motion picture projector having the aforementioned features and yet being of a simplified construction lending itself to low cost manufacturing.